Exemplary embodiments of the present invention relate to a semi-finished product arrangement, a method for the production of a fiber composite component, and use of such a semi-finished product arrangement.
For the production of a fiber composite component by molding (e.g. punch molding) of a planar semi-finished fiber composite product in a molding tool (e.g. molding press), “semi-finished product arrangements” are known from the state of the art, which comprise the semi-finished fiber composite product and multiple holding elements attached thereto and each extending beyond the edge of the semi-finished fiber composite product.
In the known methods for the production of a fiber composite component using such a semi-finished product arrangement, this semi-finished product arrangement is molded with a semi-finished fiber composite product edge that projects out of the molding tool all around. The holding elements that serve for holding the semi-finished fiber composite product during the molding process (and, if necessary, during prior heating of the semi-finished fiber composite product), in this connection, are not allowed to lie in the region of the molding tool (press region), because otherwise they would damage the tool.
A disadvantage of this state of the art is the often significant additional material expenditure for the semi-finished fiber composite product to be molded, in order to provide for the above-mentioned “projecting edge of the semi-finished fiber composite product.”
Exemplary embodiments of the present invention are directed to an improved semi-finished product arrangement, method for the production of a fiber composite component, use of such a semi-finished product arrangement, the results in the fiber composite component production being implemented with less material expenditure.
According to a first aspect of the invention, in a semi-finished product arrangement the holding elements countersunk in recesses of the semi-finished fiber composite product, in order to avoid a projection in terms of height.
This allows the edge of the semi-finished fiber composite product to run at least in part, particularly entirely within the molding tool during the molding process, the countersunk arrangement of the holding elements, however, reducing or entirely eliminating the risk of damage to or wear of the molding tool caused by the holding elements.
According to one embodiment, the recesses each possess a contour that is adapted to the contour of the holding element in question. This particularly covers the case where, seen in a top view, at most a small gap remains between the contour of the holding element in question and the contour of the recess in question. In other words, in this case the holding element contour is arranged in the recess contour without or at most with “slight play.”
In a possible embodiment variant, the recess is worked in from the lateral edge of the semi-finished fiber composite product, with a certain recess height (orthogonal to the plane of the semi-finished fiber composite product), which height is less than the height (thickness) of the semi-finished fiber composite product and greater than or equal to the height (thickness) of the holding element. After the holding element in question has been laid/pushed into place (from the side) in such a lateral recess, the surfaces, on both sides, of the holding element arranged to be countersunk are each covered by material of the semi-finished fiber composite product, and the holding element is arranged to be more or less “completely countersunk.”
In another preferred embodiment variant, the recess on one of the two flat sides of the semi-finished fiber composite product is worked in with a certain recess depth that is less, for example, than the height (thickness) of the semi-finished fiber composite product. After the holding element has been laid into place (from the side) in such a recess, an “exposed surface” of the holding element arranged to be (completely or partially) countersunk occurs.
In one embodiment, the exposed surfaces of the holding elements arranged to be countersunk are each arranged to be countersunk or at most substantially flush with the surface of the semi-finished fiber composite product, in the region bordering on the recess.
This avoids a noteworthy projection in terms of height of the holding elements and this prevents or accordingly reduces possible tool wear.
For the case that during the molding process compression of the semi-finished fiber composite product, in terms of height, also takes place, it is preferred if the exposed surfaces of the holding elements arranged to be countersunk are each countersunk with reference to the surface of the semi-finished fiber composite product, in the region bordering on the recess. This “countersunk arrangement of the exposed surfaces” can, in this connection, be adapted, in terms of extent, to the molding process to be performed, in such a manner that during the molding process, no noteworthy force (thereby causing wear) is exerted on the molding tool by the holding elements arranged to be countersunk.
In one embodiment the holding elements (or at least part thereof) are each configured as elongated holding rods or holding wires having a circular cross-section, for example, or an at least approximately square cross-section, for example. A corresponding transverse expanse or diameter in this connection can lie in the range of about 0.2 to 4 mm, for example. Such a holding wire can be angled away at its proximal end (i.e., provided for fixation on the semi-finished fiber composite product), in order to engage into a corresponding fixation recess of the semi-finished fiber composite product. Alternatively, this end can be bent to form a flat eye, for example, in order to be able to implement attachment by means of riveting.
In another embodiment, the holding elements (or at least part thereof) are each configured as elongated holding strips arranged co-planar to the plane of the semi-finished fiber composite product.
In this way, great mechanical strength (here, for example, tensile strength) is achieved at a simultaneous comparatively small height (thickness) of the holding elements.
The ratio of the width of the holding strips to the height (thickness) of the holding strips is preferably greater than 3, particularly 5, and, on the other hand, less than 100, particularly 50, for example.
In one embodiment, the holding elements are formed from a metal material (e.g., aluminum, steel, etc.). Alternatively, other materials can also be provided for this purpose, particularly plastic or plastic composite materials (e.g., plastic having a high melting point or duroplastic/glass fiber reinforced plastic).
In a preferred embodiment, the holding elements (or at least those sections of them situated within the molding tool during the later molding process) are formed from a material that is softer than the material of the molding tool used for the molding process (in order to avoid excess tool wear).
In one embodiment, the holding elements each possess a shape suitable for implementing a tension spring effect. The holding elements can have such a shape particularly in a distal section (i.e. situated at a distance from their fixation location on the semi-finished fiber composite product) of the element, which section lies outside of the molding tool during the later molding process.
In the aforementioned configuration of the holding elements as elongated holding strips, in each instance, a wave-like or zigzag-like course of the holding strips in a distal region (seen from the side) can be provided.
There are various possibilities to be considered for the fixation of the holding elements on the semi-finished fiber composite product.
Because in practice, generally only a tension effect by means of the holding elements, which “spreads out” the semi-finished fiber composite product, is required, the fixation connection can be configured, for example, as a suitable (i.e. tension-resistant) shape-fit connection. An example of this would be a holding element that engages into a corresponding fixation recess of the semi-finished fiber composite product at its proximal end, with a section that runs in the height direction of the semi-finished fiber composite product (e.g. a formed-on projection, angled portion or “hook”).
In another embodiment, the fixation connection is provided as an attachment connection, for example by means of adhesively attaching proximal sections of the holding elements, in each instance, to the semi-finished fiber composite product. For this purpose, adhesive layers can be arranged between the respective recess bottoms and the holding elements, for example, if the holding elements are arranged to be countersunk in recesses, or, if no such recesses of the semi-finished fiber composite product are provided, these layers can be provided between respective regions on a flat side of the semi-finished fiber composite product and the holding elements, for example.
In another embodiment, attachment of the holding elements is implemented, in each instance, by riveting them to the semi-finished fiber composite product. For this purpose, rivets, e.g. countersunk rivets, can be used, particularly, for example, made of a relatively soft metal material (e.g. aluminum or aluminum alloy; preferably, in any case, softer than the material of the molding tool). In this connection, the rivets or countersunk rivets can pass through attachment holes (preferably provided with a countersunk portion) of the holding elements and further through (coaxially arranged) attachment holes of the semi-finished fiber composite product. Alternatively or in addition to a countersunk portion of the attachment holes of the holding elements, the attachment holes of the semi-finished fiber composite product can also be configured with a countersunk portion.
According to a further aspect of the present invention, a method for the production of a fiber composite component by means of molding a planar semi-finished fiber composite product in a molding tool is provided, in which method a semi-finished product arrangement of a conventional or of the inventive arrangement is used, wherein during molding, the edge of the semi-finished fiber composite product runs at least in part, particularly entirely within the molding tool, and the holding elements each extend out of the molding tool.
If a semi-finished product arrangement of the type according to the invention is used in this method, then, as has already been explained, the risk of damage to or wear of the molding tool is reduced or entirely eliminated by means of the countersunk arrangement of the holding elements.
However, in the event that such a countersunk arrangement of the holding elements is not provided for in the method, it has been shown that the method can nevertheless often be carried out with at most slight wear, namely, in particular, when the holding elements are each configured as elongated holding strips, arranged co-planar to the plane of the semi-finished fiber composite product, particularly with a ratio of the width of the holding strips of more than 3, particularly more than 5. On the other hand, this ratio can be less than 100, particularly less than 50, for example.
In practice, it is probably due to the fact that such “flat” holding elements are more or less pressed into (countersunk into) the material of the semi-finished fiber composite product during the molding process that no significant wear of the molding tool occurs. In this regard, an embodiment is preferred in which the height (thickness) of the holding elements is less than 0.3 times, particularly less than 0.2 times the height (thickness) of the semi-finished fiber composite product in the region bordering on the fixation location. Once again, a shape-fit connection of the type described above, for example, can be used for fixation, or also a rivet connection with the semi-finished fiber composite product, for example, can be provided.
According to a preferred use of a semi-finished product arrangement of the type described here and/or of a method of the type described here, the production of structural components for vehicles, particularly aircraft, is provided.
According to a more specific use of a semi-finished product arrangement of the type described here and/or of a method of the type described here, the production of what are called “clips” for the production of a vehicle hull, particularly, e.g., a hull or hull section of an aircraft, composed of hull shell, stringers, frames, and clips, is provided.
In this connection, stringers are understood to be reinforcement elements running longitudinally on the inside of the hull shell (e.g. profiles), whereas the frames represent reinforcement elements that run in the circumference direction on the inside of the hull shell (e.g. profiles). In this connection, the clips are connection elements, in the meaning usual in the industry, for creating a connection between a frame and the hull shell.
Furthermore, it would also be conceivable, in the production of a vehicle hull composed of hull shell, stringers, and frames, to produce other connection elements according to the invention for connecting these components with one another, for example for creating a connection between a frame and at least one stringer, or for creating a connection between a frame and at least one stringer and the hull shell. Such a connection element or the stated clip can be connected with the components in question at the corresponding locations, for example by means of an adhesive connection or a rivet connection.